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| <article class="doc"> |
| <div class="sect1"> |
| <h2 id="functions"><a class="anchor" href="#functions"></a>Functions</h2> |
| <div class="sectionbody"> |
| <div class="paragraph"> |
| <p>CQL supports 2 main categories of functions:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p><a href="#scalar-functions">scalar functions</a> that take a number of values and produce an output</p> |
| </li> |
| <li> |
| <p><a href="#aggregate-functions">aggregate functions</a> that aggregate multiple rows resulting from a <code>SELECT</code> statement</p> |
| </li> |
| </ul> |
| </div> |
| <div class="paragraph"> |
| <p>In both cases, CQL provides a number of native "hard-coded" functions as |
| well as the ability to create new user-defined functions.</p> |
| </div> |
| <div class="admonitionblock note"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <i class="fa icon-note" title="Note"></i> |
| </td> |
| <td class="content"> |
| <div class="title">Note</div> |
| <div class="paragraph"> |
| <p>By default, the use of user-defined functions is disabled by default for |
| security concerns (even when enabled, the execution of user-defined |
| functions is sandboxed and a "rogue" function should not be allowed to |
| do evil, but no sandbox is perfect so using user-defined functions is |
| opt-in). See the <code>enable_user_defined_functions</code> in <code>cassandra.yaml</code> to |
| enable them.</p> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| <div class="paragraph"> |
| <p>A function is identifier by its name:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-bnf hljs" data-lang="bnf">function_name ::= [ keyspace_name'.' ] name</code></pre> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="scalar-functions"><a class="anchor" href="#scalar-functions"></a>Scalar functions</h3> |
| <div class="sect3"> |
| <h4 id="scalar-native-functions"><a class="anchor" href="#scalar-native-functions"></a>Native functions</h4> |
| <div class="sect4"> |
| <h5 id="cast"><a class="anchor" href="#cast"></a>Cast</h5> |
| <div class="paragraph"> |
| <p>The <code>cast</code> function can be used to converts one native datatype to |
| another.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The following table describes the conversions supported by the <code>cast</code> |
| function. Cassandra will silently ignore any cast converting a datatype |
| into its own datatype.</p> |
| </div> |
| <table class="tableblock frame-all grid-all stretch"> |
| <colgroup> |
| <col style="width: 50%;"> |
| <col style="width: 50%;"> |
| </colgroup> |
| <thead> |
| <tr> |
| <th class="tableblock halign-left valign-top">From</th> |
| <th class="tableblock halign-left valign-top">To</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>ascii</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>bigint</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>float</code>, <code>double</code>, <code>decimal</code>, <code>varint</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>boolean</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>counter</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>bigint</code>, <code>float</code>, <code>double</code>, <code>decimal</code>, |
| <code>varint</code>, <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>date</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timestamp</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>decimal</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>bigint</code>, <code>float</code>, <code>double</code>, <code>varint</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>double</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>bigint</code>, <code>float</code>, <code>decimal</code>, <code>varint</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>float</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>bigint</code>, <code>double</code>, <code>decimal</code>, <code>varint</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>inet</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>int</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>bigint</code>, <code>float</code>, <code>double</code>, <code>decimal</code>, <code>varint</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>smallint</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>int</code>, <code>bigint</code>, <code>float</code>, <code>double</code>, <code>decimal</code>, <code>varint</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>time</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>date</code>, <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeuuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timestamp</code>, <code>date</code>, <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>bigint</code>, <code>float</code>, <code>double</code>, <code>decimal</code>, |
| <code>varint</code>, <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>uuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>varint</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>tinyint</code>, <code>smallint</code>, <code>int</code>, <code>bigint</code>, <code>float</code>, <code>double</code>, <code>decimal</code>, |
| <code>text</code>, <code>varchar</code></p></td> |
| </tr> |
| </tbody> |
| </table> |
| <div class="paragraph"> |
| <p>The conversions rely strictly on Java’s semantics. For example, the |
| double value 1 will be converted to the text value '1.0'. For instance:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT avg(cast(count as double)) FROM myTable</code></pre> |
| </div> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="token"><a class="anchor" href="#token"></a>Token</h5> |
| <div class="paragraph"> |
| <p>The <code>token</code> function computes the token for a given partition key. |
| The exact signature of the token function depends on the table concerned and the partitioner used by the cluster.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The type of the arguments of the <code>token</code> depend on the partition key column type. The returned type depends on the defined partitioner:</p> |
| </div> |
| <table class="tableblock frame-all grid-all stretch"> |
| <colgroup> |
| <col style="width: 50%;"> |
| <col style="width: 50%;"> |
| </colgroup> |
| <thead> |
| <tr> |
| <th class="tableblock halign-left valign-top">Partitioner</th> |
| <th class="tableblock halign-left valign-top">Returned type</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Murmur3Partitioner</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>bigint</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">RandomPartitioner</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>varint</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">ByteOrderedPartitioner</p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>blob</code></p></td> |
| </tr> |
| </tbody> |
| </table> |
| <div class="paragraph"> |
| <p>For example, consider the following table:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">CREATE TABLE users ( |
| userid text PRIMARY KEY, |
| username text, |
| );</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>The table uses the default Murmur3Partitioner. |
| The <code>token</code> function uses the single argument <code>text</code>, because the partition key is <code>userid</code> of text type. |
| The returned type will be <code>bigint</code>.</p> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="uuid"><a class="anchor" href="#uuid"></a>Uuid</h5> |
| <div class="paragraph"> |
| <p>The <code>uuid</code> function takes no parameters and generates a random type 4 |
| uuid suitable for use in <code>INSERT</code> or <code>UPDATE</code> statements.</p> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="timeuuid-functions"><a class="anchor" href="#timeuuid-functions"></a>Timeuuid functions</h5> |
| <div class="sect5"> |
| <h6 id="now"><a class="anchor" href="#now"></a><code>now</code></h6> |
| <div class="paragraph"> |
| <p>The <code>now</code> function takes no arguments and generates, on the coordinator |
| node, a new unique timeuuid at the time the function is invoked. Note |
| that this method is useful for insertion but is largely non-sensical in |
| <code>WHERE</code> clauses.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example, a query of the form:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT * FROM myTable WHERE t = now();</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>will not return a result, by design, since the value returned by |
| <code>now()</code> is guaranteed to be unique.</p> |
| </div> |
| <div class="paragraph"> |
| <p><code>currentTimeUUID</code> is an alias of <code>now</code>.</p> |
| </div> |
| </div> |
| <div class="sect5"> |
| <h6 id="mintimeuuid-and-maxtimeuuid"><a class="anchor" href="#mintimeuuid-and-maxtimeuuid"></a><code>minTimeuuid</code> and <code>maxTimeuuid</code></h6> |
| <div class="paragraph"> |
| <p>The <code>minTimeuuid</code> function takes a <code>timestamp</code> value <code>t</code>, either a timestamp or a date string. |
| It returns a <em>fake</em> <code>timeuuid</code> corresponding to the <em>smallest</em> possible <code>timeuuid</code> for timestamp <code>t</code>. |
| The <code>maxTimeuuid</code> works similarly, but returns the <em>largest</em> possible <code>timeuuid</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT * FROM myTable |
| WHERE t > maxTimeuuid('2013-01-01 00:05+0000') |
| AND t < minTimeuuid('2013-02-02 10:00+0000');</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>will select all rows where the <code>timeuuid</code> column <code>t</code> is later than <code>'2013-01-01 00:05+0000'</code> and earlier than <code>'2013-02-02 10:00+0000'</code>. |
| The clause <code>t >= maxTimeuuid('2013-01-01 00:05+0000')</code> would still <em>not</em> select a <code>timeuuid</code> generated exactly at '2013-01-01 00:05+0000', and is essentially equivalent to <code>t > maxTimeuuid('2013-01-01 00:05+0000')</code>.</p> |
| </div> |
| <div class="admonitionblock note"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <i class="fa icon-note" title="Note"></i> |
| </td> |
| <td class="content"> |
| <div class="title">Note</div> |
| <div class="paragraph"> |
| <p>The values generated by <code>minTimeuuid</code> and <code>maxTimeuuid</code> are called <em>fake</em> UUID because they do no respect the time-based UUID generation process |
| specified by the <a href="http://www.ietf.org/rfc/rfc4122.txt">IETF RFC 4122</a>. |
| In particular, the value returned by these two methods will not be unique. |
| Thus, only use these methods for <strong>querying</strong>, not for <strong>insertion</strong>, to prevent possible data overwriting.</p> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="datetime-functions"><a class="anchor" href="#datetime-functions"></a>Datetime functions</h5> |
| <div class="sect5"> |
| <h6 id="retrieving-the-current-datetime"><a class="anchor" href="#retrieving-the-current-datetime"></a>Retrieving the current date/time</h6> |
| <div class="paragraph"> |
| <p>The following functions can be used to retrieve the date/time at the |
| time where the function is invoked:</p> |
| </div> |
| <table class="tableblock frame-all grid-all stretch"> |
| <colgroup> |
| <col style="width: 50%;"> |
| <col style="width: 50%;"> |
| </colgroup> |
| <thead> |
| <tr> |
| <th class="tableblock halign-left valign-top">Function name</th> |
| <th class="tableblock halign-left valign-top">Output type</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>currentTimestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timestamp</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>currentDate</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>date</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>currentTime</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>time</code></p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>currentTimeUUID</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeUUID</code></p></td> |
| </tr> |
| </tbody> |
| </table> |
| <div class="paragraph"> |
| <p>For example the last two days of data can be retrieved using:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT * FROM myTable WHERE date >= currentDate() - 2d;</code></pre> |
| </div> |
| </div> |
| </div> |
| <div class="sect5"> |
| <h6 id="time-conversion-functions"><a class="anchor" href="#time-conversion-functions"></a>Time conversion functions</h6> |
| <div class="paragraph"> |
| <p>A number of functions are provided to convert a <code>timeuuid</code>, a <code>timestamp</code> or a <code>date</code> into another <code>native</code> type.</p> |
| </div> |
| <table class="tableblock frame-all grid-all stretch"> |
| <colgroup> |
| <col style="width: 33.3333%;"> |
| <col style="width: 33.3333%;"> |
| <col style="width: 33.3334%;"> |
| </colgroup> |
| <thead> |
| <tr> |
| <th class="tableblock halign-left valign-top">Function name</th> |
| <th class="tableblock halign-left valign-top">Input type</th> |
| <th class="tableblock halign-left valign-top">Description</th> |
| </tr> |
| </thead> |
| <tbody> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toDate</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeuuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>timeuuid</code> argument into a <code>date</code> type</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toDate</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>timestamp</code> argument into a <code>date</code> type</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toTimestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeuuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>timeuuid</code> argument into a <code>timestamp</code> type</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toTimestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>date</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>date</code> argument into a <code>timestamp</code> type</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toUnixTimestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeuuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>timeuuid</code> argument into a <code>bigInt</code> raw value</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toUnixTimestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>timestamp</code> argument into a <code>bigInt</code> raw value</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>toUnixTimestamp</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>date</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Converts the <code>date</code> argument into a <code>bigInt</code> raw value</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>dateOf</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeuuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Similar to <code>toTimestamp(timeuuid)</code> (DEPRECATED)</p></td> |
| </tr> |
| <tr> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>unixTimestampOf</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock"><code>timeuuid</code></p></td> |
| <td class="tableblock halign-left valign-top"><p class="tableblock">Similar to <code>toUnixTimestamp(timeuuid)</code> (DEPRECATED)</p></td> |
| </tr> |
| </tbody> |
| </table> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="blob-conversion-functions"><a class="anchor" href="#blob-conversion-functions"></a>Blob conversion functions</h5> |
| <div class="paragraph"> |
| <p>A number of functions are provided to convert the native types into |
| binary data, or a <code>blob</code>. |
| For every <a href="types.html#native-types" class="page">type</a> supported by CQL, the function <code>typeAsBlob</code> takes a argument of type <code>type</code> and returns it as a <code>blob</code>. |
| Conversely, the function <code>blobAsType</code> takes a 64-bit <code>blob</code> argument and converts it to a <code>bigint</code> value. |
| For example, <code>bigintAsBlob(3)</code> returns <code>0x0000000000000003</code> and <code>blobAsBigint(0x0000000000000003)</code> returns <code>3</code>.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="user-defined-scalar-functions"><a class="anchor" href="#user-defined-scalar-functions"></a>User-defined functions</h4> |
| <div class="paragraph"> |
| <p>User-defined functions (UDFs) execute user-provided code in Cassandra. |
| By default, Cassandra supports defining functions in <em>Java</em> and <em>JavaScript</em>. |
| Support for other JSR 223 compliant scripting languages, such as Python, Ruby, and Scala, is possible by adding a JAR to the classpath.</p> |
| </div> |
| <div class="paragraph"> |
| <p>UDFs are part of the Cassandra schema, and are automatically propagated to all nodes in the cluster. |
| UDFs can be <em>overloaded</em>, so that multiple UDFs with different argument types can have the same function name.</p> |
| </div> |
| <div class="admonitionblock note"> |
| <table> |
| <tr> |
| <td class="icon"> |
| <i class="fa icon-note" title="Note"></i> |
| </td> |
| <td class="content"> |
| <div class="title">Note</div> |
| <div class="paragraph"> |
| <p><em>JavaScript</em> user-defined functions have been deprecated. They are planned for removal |
| in the next major release.</p> |
| </div> |
| </td> |
| </tr> |
| </table> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">CREATE FUNCTION sample ( arg int ) ...; |
| CREATE FUNCTION sample ( arg text ) ...;</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>UDFs are susceptible to all of the normal problems with the chosen programming language. |
| Accordingly, implementations should be safe against null pointer exceptions, illegal arguments, or any other potential source of exceptions. |
| An exception during function execution will result in the entire statement failing. |
| Valid queries for UDF use are <code>SELECT</code>, <code>INSERT</code> and <code>UPDATE</code> statements.</p> |
| </div> |
| <div class="paragraph"> |
| <p><em>Complex</em> types like collections, tuple types and user-defined types are valid argument and return types in UDFs. |
| Tuple types and user-defined types use the DataStax Java Driver conversion functions. |
| Please see the Java Driver documentation for details on handling tuple types and user-defined types.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Arguments for functions can be literals or terms. |
| Prepared statement placeholders can be used, too.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Note the use the double dollar-sign syntax to enclose the UDF source code.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">CREATE FUNCTION some_function ( arg int ) |
| RETURNS NULL ON NULL INPUT |
| RETURNS int |
| LANGUAGE java |
| AS $$ return arg; $$; |
| |
| SELECT some_function(column) FROM atable ...; |
| UPDATE atable SET col = some_function(?) ...; |
| |
| CREATE TYPE custom_type (txt text, i int); |
| CREATE FUNCTION fct_using_udt ( udtarg frozen ) |
| RETURNS NULL ON NULL INPUT |
| RETURNS text |
| LANGUAGE java |
| AS $$ return udtarg.getString("txt"); $$;</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>The implicitly available <code>udfContext</code> field (or binding for script UDFs) provides the necessary functionality to create new UDT and tuple values:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">CREATE TYPE custom_type (txt text, i int); |
| CREATE FUNCTION fct\_using\_udt ( somearg int ) |
| RETURNS NULL ON NULL INPUT |
| RETURNS custom_type |
| LANGUAGE java |
| AS $$ |
| UDTValue udt = udfContext.newReturnUDTValue(); |
| udt.setString("txt", "some string"); |
| udt.setInt("i", 42); |
| return udt; |
| $$;</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>The definition of the <code>UDFContext</code> interface can be found in the Apache Cassandra source code for <code>org.apache.cassandra.cql3.functions.UDFContext</code>.</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">public interface UDFContext |
| { |
| UDTValue newArgUDTValue(String argName); |
| UDTValue newArgUDTValue(int argNum); |
| UDTValue newReturnUDTValue(); |
| UDTValue newUDTValue(String udtName); |
| TupleValue newArgTupleValue(String argName); |
| TupleValue newArgTupleValue(int argNum); |
| TupleValue newReturnTupleValue(); |
| TupleValue newTupleValue(String cqlDefinition); |
| }</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Java UDFs already have some imports for common interfaces and classes defined. These imports are:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-java hljs" data-lang="java">import java.nio.ByteBuffer; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.Set; |
| import org.apache.cassandra.cql3.functions.UDFContext; |
| import com.datastax.driver.core.TypeCodec; |
| import com.datastax.driver.core.TupleValue; |
| import com.datastax.driver.core.UDTValue;</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>Please note, that these convenience imports are not available for script UDFs.</p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="create-function-statement"><a class="anchor" href="#create-function-statement"></a>CREATE FUNCTION statement</h4> |
| <div class="paragraph"> |
| <p>Creating a new user-defined function uses the <code>CREATE FUNCTION</code> statement:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-bnf hljs" data-lang="bnf">create_function_statement::= CREATE [ OR REPLACE ] FUNCTION [ IF NOT EXISTS] |
| function_name '(' arguments_declaration ')' |
| [ CALLED | RETURNS NULL ] ON NULL INPUT |
| RETURNS cql_type |
| LANGUAGE identifier |
| AS string arguments_declaration: identifier cql_type ( ',' identifier cql_type )*</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">CREATE OR REPLACE FUNCTION somefunction(somearg int, anotherarg text, complexarg frozen<someUDT>, listarg list) |
| RETURNS NULL ON NULL INPUT |
| RETURNS text |
| LANGUAGE java |
| AS $$ |
| // some Java code |
| $$; |
| |
| CREATE FUNCTION IF NOT EXISTS akeyspace.fname(someArg int) |
| CALLED ON NULL INPUT |
| RETURNS text |
| LANGUAGE java |
| AS $$ |
| // some Java code |
| $$;</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p><code>CREATE FUNCTION</code> with the optional <code>OR REPLACE</code> keywords creates either a function or replaces an existing one with the same signature. |
| A <code>CREATE FUNCTION</code> without <code>OR REPLACE</code> fails if a function with the same signature already exists. |
| If the optional <code>IF NOT EXISTS</code> keywords are used, the function will only be created only if another function with the same signature does not |
| exist. |
| <code>OR REPLACE</code> and <code>IF NOT EXISTS</code> cannot be used together.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Behavior for <code>null</code> input values must be defined for each function:</p> |
| </div> |
| <div class="ulist"> |
| <ul> |
| <li> |
| <p><code>RETURNS NULL ON NULL INPUT</code> declares that the function will always return <code>null</code> if any of the input arguments is <code>null</code>.</p> |
| </li> |
| <li> |
| <p><code>CALLED ON NULL INPUT</code> declares that the function will always be executed.</p> |
| </li> |
| </ul> |
| </div> |
| <div class="sect4"> |
| <h5 id="function-signature"><a class="anchor" href="#function-signature"></a>Function Signature</h5> |
| <div class="paragraph"> |
| <p>Signatures are used to distinguish individual functions. The signature consists of a fully-qualified function name of the <keyspace>.<function_name> and a concatenated list of all the argument types.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Note that keyspace names, function names and argument types are subject to the default naming conventions and case-sensitivity rules.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Functions belong to a keyspace; if no keyspace is specified, the current keyspace is used. |
| User-defined functions are not allowed in the system keyspaces.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="drop-function-statement"><a class="anchor" href="#drop-function-statement"></a>DROP FUNCTION statement</h4> |
| <div class="paragraph"> |
| <p>Dropping a function uses the <code>DROP FUNCTION</code> statement:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-bnf hljs" data-lang="bnf">drop_function_statement::= DROP FUNCTION [ IF EXISTS ] function_name [ '(' arguments_signature ')' ] |
| arguments_signature::= cql_type ( ',' cql_type )*</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">DROP FUNCTION myfunction; |
| DROP FUNCTION mykeyspace.afunction; |
| DROP FUNCTION afunction ( int ); |
| DROP FUNCTION afunction ( text );</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>You must specify the argument types of the function, the arguments_signature, in the drop command if there are multiple overloaded functions with the same name but different signatures. |
| <code>DROP FUNCTION</code> with the optional <code>IF EXISTS</code> keywords drops a function if it exists, but does not throw an error if it doesn’t.</p> |
| </div> |
| </div> |
| </div> |
| <div class="sect2"> |
| <h3 id="aggregate-functions"><a class="anchor" href="#aggregate-functions"></a>Aggregate functions</h3> |
| <div class="paragraph"> |
| <p>Aggregate functions work on a set of rows. |
| Values for each row are input, to return a single value for the set of rows aggregated.</p> |
| </div> |
| <div class="paragraph"> |
| <p>If <code>normal</code> columns, <code>scalar functions</code>, <code>UDT</code> fields, <code>writetime</code>, or <code>ttl</code> are selected together with aggregate functions, the values |
| returned for them will be the ones of the first row matching the query.</p> |
| </div> |
| <div class="sect3"> |
| <h4 id="native-aggregates"><a class="anchor" href="#native-aggregates"></a>Native aggregates</h4> |
| <div class="sect4"> |
| <h5 id="count-function"><a class="anchor" href="#count-function"></a>Count</h5> |
| <div class="paragraph"> |
| <p>The <code>count</code> function can be used to count the rows returned by a query.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT COUNT (*) FROM plays; |
| SELECT COUNT (1) FROM plays;</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>It also can count the non-null values of a given column:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT COUNT (scores) FROM plays;</code></pre> |
| </div> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="max-and-min"><a class="anchor" href="#max-and-min"></a>Max and Min</h5> |
| <div class="paragraph"> |
| <p>The <code>max</code> and <code>min</code> functions compute the maximum and the minimum value returned by a query for a given column.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT MIN (players), MAX (players) FROM plays WHERE game = 'quake';</code></pre> |
| </div> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="sum"><a class="anchor" href="#sum"></a>Sum</h5> |
| <div class="paragraph"> |
| <p>The <code>sum</code> function sums up all the values returned by a query for a given column.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT SUM (players) FROM plays;</code></pre> |
| </div> |
| </div> |
| </div> |
| <div class="sect4"> |
| <h5 id="avg"><a class="anchor" href="#avg"></a>Avg</h5> |
| <div class="paragraph"> |
| <p>The <code>avg</code> function computes the average of all the values returned by a query for a given column.</p> |
| </div> |
| <div class="paragraph"> |
| <p>For example:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">SELECT AVG (players) FROM plays;</code></pre> |
| </div> |
| </div> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="user-defined-aggregates-functions"><a class="anchor" href="#user-defined-aggregates-functions"></a>User-Defined Aggregates (UDAs)</h4> |
| <div class="paragraph"> |
| <p>User-defined aggregates allow the creation of custom aggregate functions. |
| User-defined aggregates can be used in <code>SELECT</code> statement.</p> |
| </div> |
| <div class="paragraph"> |
| <p>Each aggregate requires an <em>initial state</em> of type <code>STYPE</code> defined with the <code>INITCOND`value (default value: `null</code>). |
| The first argument of the state function must have type <code>STYPE</code>. |
| The remaining arguments of the state function must match the types of the user-defined aggregate arguments. |
| The state function is called once for each row, and the value returned by the state function becomes the new state. |
| After all rows are processed, the optional <code>FINALFUNC</code> is executed with last state value as its argument.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>STYPE</code> value is mandatory in order to distinguish possibly overloaded versions of the state and/or final function, since the |
| overload can appear after creation of the aggregate.</p> |
| </div> |
| <div class="paragraph"> |
| <p>A complete working example for user-defined aggregates (assuming that a |
| keyspace has been selected using the <code>USE</code> statement):</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">CREATE OR REPLACE FUNCTION test.averageState(state tuple<int,bigint>, val int) |
| CALLED ON NULL INPUT |
| RETURNS tuple |
| LANGUAGE java |
| AS $$ |
| if (val != null) { |
| state.setInt(0, state.getInt(0)+1); |
| state.setLong(1, state.getLong(1)+val.intValue()); |
| } |
| return state; |
| $$; |
| |
| CREATE OR REPLACE FUNCTION test.averageFinal (state tuple<int,bigint>) |
| CALLED ON NULL INPUT |
| RETURNS double |
| LANGUAGE java |
| AS $$ |
| double r = 0; |
| if (state.getInt(0) == 0) return null; |
| r = state.getLong(1); |
| r /= state.getInt(0); |
| return Double.valueOf(r); |
| $$; |
| |
| CREATE OR REPLACE AGGREGATE test.average(int) |
| SFUNC averageState |
| STYPE tuple |
| FINALFUNC averageFinal |
| INITCOND (0, 0); |
| |
| CREATE TABLE test.atable ( |
| pk int PRIMARY KEY, |
| val int |
| ); |
| |
| INSERT INTO test.atable (pk, val) VALUES (1,1); |
| INSERT INTO test.atable (pk, val) VALUES (2,2); |
| INSERT INTO test.atable (pk, val) VALUES (3,3); |
| INSERT INTO test.atable (pk, val) VALUES (4,4); |
| |
| SELECT test.average(val) FROM atable;</code></pre> |
| </div> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="create-aggregate-statement"><a class="anchor" href="#create-aggregate-statement"></a>CREATE AGGREGATE statement</h4> |
| <div class="paragraph"> |
| <p>Creating (or replacing) a user-defined aggregate function uses the |
| <code>CREATE AGGREGATE</code> statement:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-bnf hljs" data-lang="bnf">create_aggregate_statement ::= CREATE [ OR REPLACE ] AGGREGATE [ IF NOT EXISTS ] |
| function_name '(' arguments_signature')' |
| SFUNC function_name |
| STYPE cql_type: |
| [ FINALFUNC function_name] |
| [ INITCOND term ]</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>See above for a complete example.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>CREATE AGGREGATE</code> command with the optional <code>OR REPLACE</code> keywords creates either an aggregate or replaces an existing one with the same |
| signature. |
| A <code>CREATE AGGREGATE</code> without <code>OR REPLACE</code> fails if an aggregate with the same signature already exists. |
| The <code>CREATE AGGREGATE</code> command with the optional <code>IF NOT EXISTS</code> keywords creates an aggregate if it does not already exist. |
| The <code>OR REPLACE</code> and <code>IF NOT EXISTS</code> phrases cannot be used together.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>STYPE</code> value defines the type of the state value and must be specified. |
| The optional <code>INITCOND</code> defines the initial state value for the aggregate; the default value is <code>null</code>. |
| A non-null <code>INITCOND</code> must be specified for state functions that are declared with <code>RETURNS NULL ON NULL INPUT</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>SFUNC</code> value references an existing function to use as the state-modifying function. |
| The first argument of the state function must have type <code>STYPE</code>. |
| The remaining arguments of the state function must match the types of the user-defined aggregate arguments. |
| The state function is called once for each row, and the value returned by the state function becomes the new state. |
| State is not updated for state functions declared with <code>RETURNS NULL ON NULL INPUT</code> and called with <code>null</code>. |
| After all rows are processed, the optional <code>FINALFUNC</code> is executed with last state value as its argument. |
| It must take only one argument with type <code>STYPE</code>, but the return type of the <code>FINALFUNC</code> may be a different type. |
| A final function declared with <code>RETURNS NULL ON NULL INPUT</code> means that the aggregate’s return value will be <code>null</code>, if the last state is <code>null</code>.</p> |
| </div> |
| <div class="paragraph"> |
| <p>If no <code>FINALFUNC</code> is defined, the overall return type of the aggregate function is <code>STYPE</code>. |
| If a <code>FINALFUNC</code> is defined, it is the return type of that function.</p> |
| </div> |
| </div> |
| <div class="sect3"> |
| <h4 id="drop-aggregate-statement"><a class="anchor" href="#drop-aggregate-statement"></a>DROP AGGREGATE statement</h4> |
| <div class="paragraph"> |
| <p>Dropping an user-defined aggregate function uses the <code>DROP AGGREGATE</code> |
| statement:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-bnf hljs" data-lang="bnf">drop_aggregate_statement::= DROP AGGREGATE [ IF EXISTS ] function_name[ '(' arguments_signature ')' |
| ]</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>For instance:</p> |
| </div> |
| <div class="listingblock"> |
| <div class="content"> |
| <pre class="highlightjs highlight"><code class="language-cql hljs" data-lang="cql">DROP AGGREGATE myAggregate; |
| DROP AGGREGATE myKeyspace.anAggregate; |
| DROP AGGREGATE someAggregate ( int ); |
| DROP AGGREGATE someAggregate ( text );</code></pre> |
| </div> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>DROP AGGREGATE</code> statement removes an aggregate created using <code>CREATE AGGREGATE</code>. |
| You must specify the argument types of the aggregate to drop if there are multiple overloaded aggregates with the same name but a |
| different signature.</p> |
| </div> |
| <div class="paragraph"> |
| <p>The <code>DROP AGGREGATE</code> command with the optional <code>IF EXISTS</code> keywords drops an aggregate if it exists, and does nothing if a function with the |
| signature does not exist.</p> |
| </div> |
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